Heinze, B. and Fussi, B. 2017. Pre-disease Levels of Genetic Diversity and Differentiation among Common Ash (Fraxinus excelsior L.) Seedlots in Austria. Baltic Forestry 23(1): 198-208.

   Ash is an important component of forestry in Austria; its loss due to the dieback disease would be a great challenge for many forest owners. We investigated seed material that was harvested in 2001, just prior to the onset of the disease. Seeds from at least ten (allegedly) separate trees per stand were obtained from commercial harvest lots, from six different stands in Austria. The separate sampling from at least ten seed-bearing trees of ash is a legal requirement in Austria. Levels of genetic differentiation on the basis of six microsatellite markers were low, but somewhat higher than in other typical European forest trees. Stands along the Danube river seemed to share more genetic similarity with each other than with two stands in the Alps. In comparison, within the stands, most single tree seed lots were highly differentiated and they mostly fitted to the stands of origin with their genetic patterns. An attempt was made at reconstructing the unknown genotypes of the mother trees of the seeds from the offspring data. This led to the presumable identification of cases where these mother trees shared more alleles than expected, and their seed lots were closer genetically than on average. It also revealed cases where single seeds did not fit into their lot genetically (as defined by Mendelian rules). The data reported here confirm that detailed information on the genetic background of seed can be obtained from such structured samples, supporting law enforcement. It further confirms that harvesting from a minimum of ten trees leads to seed that more comprehensively reflects levels of genetic diversity in the whole stand. The data presented can be used as a baseline for investigating any genetic effects of the progressing disease in the future.

Keywords: Fraxinus excelsior, Hymenoscyphus fraxineus, microsatellite markers, genetic diversity, seed, genetic differentiation, forest reproductive material.